(1) Field of the Invention
The present invention pertains to a venting system for a manually operated, liquid dispensing trigger sprayer. More specifically, the present invention pertains to improvements to a venting system of a manually operated trigger sprayer that vents the interior of a liquid container connected to the trigger sprayer. For the most part, the construction of the trigger sprayer is typical. The improvement comprises a vent chamber that surrounds the pump chamber and a vent piston that surrounds the pump piston. The vent piston is received in the vent chamber for reciprocating movements with the pump piston in the pump chamber. The reciprocating movement of the vent piston alternatively opens the vent chamber to the exterior environment of the trigger sprayer and thereby vents the interior of the liquid container connected to the trigger sprayer, and closes the vent chamber thereby sealing the interior of the liquid container from the exterior environment. The interior of the vent chamber has a novel configuration where the interior diameter of the vent chamber gets larger as the vent chamber extends from a forward portion of the vent chamber toward a rearward portion of the vent chamber. This reduces the drag or friction between the peripheral sealing edge of the vent piston and the interior surface of the vent chamber as the vent piston moves from the forward portion of the vent chamber toward the rearward portion of the vent chamber.
(2) Description of the Related Art
A typical manually operated liquid dispensing trigger sprayer comprises a sprayer housing that has a nozzle for dispensing liquid, a trigger mounted on the sprayer housing for movement of the trigger relevant to the housing, a pump chamber on the housing, and a pump piston operatively connected to the trigger and received in the pump chamber for reciprocating movement of the piston in the pump chamber in response to manual movement of the trigger, and a connector attaching the trigger sprayer to a liquid container. The reciprocating movement of the pump piston in the pump chamber alternately draws liquid from the liquid container into the pump chamber, and then pumps the liquid out of the pump chamber and dispenses the liquid through the nozzle of the sprayer housing as a spray or stream.
Trigger sprayers of this type are often provided with some system of venting the interior of the liquid container connected to the trigger sprayer. This allows air to enter the container interior and occupy that portion of the internal volume of the container that is vacated by the liquid dispensed from the container by the trigger sprayer.
Many different types of trigger sprayer venting systems have been developed in the prior art. One type of venting system employs a resilient diaphragm valve that is positioned in the interior of the sprayer housing covering over a vent hole in the sprayer housing. The vent hole communicates the interior of the sprayer housing and the interior of the connected liquid container with the exterior environment of the sprayer. A plunger is provided on the trigger member of the trigger sprayer. The plunger projects from the bottom of the pump piston rod and curves toward the sprayer housing with a distal end of the plunger being positioned just outside of the vent hole. On manual manipulation of the trigger, the plunger end is inserted through the vent hole and engages the diaphragm valve, displacing the diaphragm valve from its position over the vent hole. This vents the interior of the liquid container. On the return movement of the trigger the plunger is retracted out of the vent hole and the resilience of the diaphragm valve allows it to resume its position over the vent hole.
However, this prior art venting system has been found to be disadvantaged in that repeated use of the trigger sprayer causes repeated displacement of the diaphragm valve from the sprayer vent hole. The resiliency of the diaphragm valve is effected by these repeated displacements and the valve is no longer able to immediately reposition itself over the vent hole once the plunger is retracted from the vent hole. This can result in liquid leaking from the container through the vent hole should the container and trigger sprayer be knocked over on one side before the diaphragm valve repositions itself over the vent hole. In addition, the plunger projecting from the piston rod is considered by many to detract from the appearance of the sprayer and is undesirable.
Another type of venting system employs a vent cylinder on the sprayer housing and a vent piston operatively connected to the trigger of the trigger sprayer. The vent piston, like the previously described plunger, projects from the pump piston rod. The vent hole is positioned in the side of the vent cylinder and one or more small ribs are formed on the interior surface of the vent cylinder in the area of the vent hole. The vent piston curves beneath the pump piston rod and extends into the vent cylinder where the vent piston engages in a sliding, sealing engagement with the interior surface of the vent cylinder. As the trigger is manipulated, the vent piston is pushed through the vent cylinder toward the vent hole and the ribs. The ribs engage with the periphery of the vent piston and displace the periphery from the interior surface of the vent cylinder, thereby communicating the exterior environment of the trigger sprayer around the piston and through the vent cylinder and the vent hole to the interior of the liquid container.
This venting system has been found to be disadvantaged in that is has the same unappealing appearance of the plunger. Also, after repeated use of the trigger sprayer, the ribs in the vent cylinder have a tendency to deform the resilient material around the periphery of the vent piston. This detracts from the ability of the vent piston to seal against the interior surface of the vent cylinder, and can result in leakage of liquid from the liquid container through the vent cylinder.
Trigger sprayer designs have eliminated the projecting plunger or vent piston rod that detracts from the overall appearance of the trigger sprayer. These designs employ a vent piston that is coaxial with the pump piston of the trigger sprayer, and is moved by the pump piston rod of the trigger sprayer. The vent piston is moved through a vent chamber that is coaxial with the trigger sprayer pump chamber. This double piston design is more desirable because it eliminates the separate plunger arm or vent piston arm from the pump piston rod.
However, the sliding engagement or rubbing of the vent piston peripheral sealing surface across the cylindrical interior surface of the vent chamber as the trigger sprayer pump is operated often causes swelling of the material of the vent piston. This swelling of the vent piston can bind the vent piston in the vent chamber, making it difficult or uncomfortable to push the vent piston into the vent chamber, and at times preventing the vent piston from being pushed back out of the vent chamber by the pump spring. What is needed to overcome this disadvantage of trigger sprayers having coaxial pump and vent chambers is a redesign of the venting system that eliminates the cause of vent piston swelling, and thereby prevents binding of the vent piston in the vent chamber.